§ 11-94. Pavement section design for land developments.

(a)

Street Classifications for Pavement Design. The street classifications contained below shall be used to select the Street Geometrics contained in Table 1 of Appendix A and the Pavement Structure contained in Table 2 of Appendix A. Both of the appendices referenced are located in Part II, Technical Provisions.

Note: In this Article, the following street classifications by traffic and eighteen (18) kip EALs are used primarily to determine the structural pavement sections. These street classifications should not be confused with the Functional Street Classifications.

Each street shall be classified by function and/or traffic in one (1) of the following classes:

(1)

Class I—light residential: This would be rural residential streets and drives which have light traffic and little or no truck traffic, short dead-end streets, and possibly short cross streets with less than fifty (50) vehicles per day and not more than five (5) average eighteen-kip EALs per day, or not more than thirty-six thousand five hundred (36,500) total eighteen (18) kip EALs during the twenty-year design period.

(2)

Class II—residential, minor residential collector and light commercial: This would include (a) residential subdivision streets with no through traffic; (b) cross streets in the established street system; (c) light commercial streets in a small commercial area. These streets would have an average of fifty (50) to two hundred fifty (250) vehicles per day and not more than ten (10) average eighteen (18) kip EALs per day, or not more than seventy-three thousand (73,000) total kip EALs during the twenty-year design period.

(3)

Class III—residential collector and commercial streets: This would include (a) the major streets in a residential subdivision used to get to the through streets or highway; collectors will have the right-of-way over the above Class I and II streets; and (b) commercial streets. They would have an average of two hundred fifty (250) to five hundred (500) vehicles per day and not more than forty (40) average eighteen (18) kip EALs per day, or not more than two hundred ninety-two thousand (292,000) total eighteen (18) kip EALs during the twenty-year design period.

(4)

Class IV—minor residential arterial, heavy commercial, and light industrial streets: These streets would include (a) through streets in a residential subdivision; (b) heavy commercial streets; and (c) light industrial streets. They would have an average of five hundred (500) to eight hundred fifty (850) vehicles per day and not more than eighty (80) average kip EALs per day, or not more than five hundred eighty-four thousand (584,000) total kip EALs during the twenty-year design period.

(5)

Class V: All higher class streets and highways, or any time the eighty (80) average eighteen (18) kip EALs or the five hundred eighty-four thousand (584,000) average eighteen (18) kip EALs are expected to be exceeded, formal design procedures shall be used for each individual street. The PCA, TAI, AASHTO, or other recognized design procedures may be used. The design for each street or highway shall be approved by the County Road Superintendent.

*** ADT may be estimated at the rate of five (5) round trips per resident or dwelling unit.

*** EALs for Class I and II streets based on one hundred (100) percent of the one-way ADT times a load factor of 0.09 for single-unit trucks, plus five (5) percent of the one-way ADT times a load factor of 1.00 for multiple-unit trucks.

*** EALs for Class III and IV streets are based on one hundred (100) percent of the one-way ADT times a load factor of 0.09 for single-unit trucks, plus ten (10) percent of the one-way ADT times a load factor of 1.00 for multiple-unit trucks.

(b)

Soil Classifications: The subgrade soils shall be classified according to the Group Index Classification into the following three (3) major soil types:

(1)

Sands and Gravels: A-1, A-2, and A-3 Group Index. These are nonplastic materials with gravel and sand-size material.

(2)

Silts: A-4 and A-6 Group Index. The A-4 soil is a minus-40 sieve size which has an LL less than 40 and a PI less than 10. The A-6 soil is a minus-40 sieve material with an LL less than 40 and a PI more than 10. Both soils have very little clay.

(3)

Clays: A-5, A-7 and A-7-6 Group Index. These are the clays and have an LL greater than 40 and an PI greater than 10. The AS Group Index classification soils have an LL greater than 40 and a PI less than 10. A-7 Group Index soils are very poor soils which should be avoided if possible.

(c)

Pavement Sections: The pavement sections for Class I, II, III and IV streets shall meet or exceed the following requirements:

(1)

All streets shall be classified according to traffic and subgrade soil type. The results of the sieve analysis and LL and PI test run during the construction of the subgrade shall be used to verify the soil type used in the pavement design. If the soil type changes, the pavement structure shall be redesigned accordingly. It is strongly recommended that the engineer have preliminary sieve analysis and LL and PI tests performed before detailed plans and specifications for the streets are prepared. Copies of all test results shall be provided to the County Road Superintendent.

(2)

Regardless of the design procedures used, the proposed pavement sections for Class I, II, III and IV streets shall be equal to or exceed the minimum pavement sections shown in Table 2, Minimum Pavement Sections, of Appendix A, Part II, Technical Provisions, for the particular street classification and soil type, with the following exceptions:

a.

A pavement structure of six (6) to eight (8) inches of compacted crushed stone base and a double bituminous surface treatment may be approved for residential streets and county roads with light traffic and little or no truck traffic. Such conditions may occur in the following: (a) small rural subdivisions and mobile home parks; (b) rural subdivisions with large three- to five-acre lots; or (c) existing minor county roads meeting these criteria.

b.

Paved roads are required in all developments except for those which qualify to be built as private roads.

(3)

Formal design procedures, such as the PCA, TAI, AASHTO, shall be used for all Class V and higher streets, or when the projected daily eighteen (18) kip EALs load exceeds eighty (80), or when the total eighteen (18) kip EALs for the twenty-year design period exceeds five hundred eighty-four thousand (584,000).

(Ord. No. 91-9, Art. 1, § 3.09, 4-11-91; Ord. No. 99-32, Art. 1, 7-8-99; Ord. No. 2006-47, Art. 1, 8-10-06)